Prior Art
Known structures or members such as casts and splints for orthopedic and athletic purposes for fixating, supporting and protecting portions of a body generally include hardenable compositions used alone, or alternatively, composites of a hardenable composition applied to a substrate such as a textile, a knit or a porous plastic layer.
Hardenable compositions used alone can include such materials as super linear polyesters such as t-polyisoprene, polycaprolactone, poly 1, 6-hexamethylene azipate, etc; polymer melts such as polyvinyl chloride, polymer alloy, etc; and thermoplastic resins having a low melting point and rigidity at ambient or normal temperatures. Such hardenable compositions are generally provided in sheets or plates having a thickness of about 1-5 mm and when heated can be worked and formed to conform to the shape of a body portion such as a portion of an arm or a leg. Limitations, however, associated with the use of hardenable compositions alone include a relatively heavy weight, a requirement of perforation thereof for the passage of air therethrough, and when overheated, such hardenable compositions alone can stretch and elongate due to their own weight so as to impair modeling or forming of the hardenable composition to a particular body portion. Due to such limitations, the hardenable compositions alone are generally of only limited usefulness.
Hardenable compositions for applying to a substrate such as a fabric, a knit or a porous plastic sheet can include a thermoplastic resin, for instance, a light curable resin that is cured when exposed to a specific wave length of light; or a plaster compound for instance of a gypseous base that is cured when exposed to water; or a water curing urethane resin that contains as its main component a compound having two (2) or more free NCO groups within its molecule such as a urethane prepolymer. Such hardenable compositions can be applied to a tape or sheet of substrate having a coarse mesh texture and composed of such materials as cotton, polyester, polypropylene, glass fibers or carbon fibers. Such substrates are generally formed by knitting high modulus fibers such as glass, polyester, polypropyrene or other fibers into textiles having weave patterns such as a marquisette stitch, an atlas stitch, a denbigh stitch, a plain stitch, a rib stitch, a purl stitch or a plain weave pattern, or by modifying those basic patterns, or by knitting with elastomer yarns or finished yarns as insert yarns or system yarns.
Numerous methods for forming substrates including glass fibers therein as suggested above have been proposed. Such known methods include using high elasticity fibers such as glass fibers combined with elastomer fibers in such a way that the elastomer fibers are introduced lengthwise so as to be stretchable by 40-200% in a longitudinal direction thereby making it possible to improve adaptability of the textile while maintaining the strength of the glass fibers, as disclosed in U.S. Pat. No. 4,668,563. Another known method uses glass fibers having an initial elasticity of at least 0.56.times.10.sup.6 kg/cm.sup.2 woven into a mesh having from 3-31 openings/cm.sup.2, which results in a material which can be hardened to a particular set strength within a short period of time and which retains porosity, as disclosed in PCT Patent No. W081/00671. Still another method uses a cloth sheet composed of glass fibers which cloth sheet has a plurality of protrusions on one of its surfaces thereby improving the lamination properties thereof, as disclosed in Japanese Unexamined Patent Application Publication No. 3-45254. Although those substrates utilizing glass fibers such as disclosed above gain a requisite strength when hardened, they also suffer from a number of shortcomings, namely, high cost and lack of transparency to X-rays making such glass fiber substrates disadvantageous for radiological diagnosis. Further, when such glass fiber substrates are formed having fluffs of fibers extending therefrom, the fluffs when hardened can become pointed like needles and can prick the skin and also scratch clothing. The edge of hardened substrates can also be irritating to the skin. Still further, when a window through the hardened structure is opened to enable treatment during recovery, or the cast or other structure is removed for remission, cutting wastes can be produced that can irritate the skin and cause dermatitis. In addition, such used or wasted casts are incombustible, such that special treatment is require for disposal thereof.
Numerous methods for using natural and synthetic fibers such as cotton, polyester, polyethylene and the like as substrates have also been proposed. For instance, a raschel fabric of natural or synthetic fibers can be formed with the ratio of the average interval between two adjacent wales against the corresponding interval between two adjacent courses being less than 1 to 5, thereby improving the X-ray transparency and the cross-sectional expandability and strength, as disclosed in U.S. Pat. No. 4,572,171. Another known substrate can be formed from nonelastic fibers, or fibers of a low elasticity, with elastic fibers introduced lengthwise, thereby providing the substrate with proper adaptability, sufficient rigidity, low fragility and sufficient durability, as disclosed in EP 0326285A2. Sill another substrate can be formed from less water-absorbing yarns of 400-1500 denier woven into a textile substrate with openings each of about 0.15 to 0.25 square inch, so that such substrate is strong, can be thinly coated with hardenable composition, and can have a good air permeability and X-ray transparency, as disclosed in U.S. Pat. No. 4,427,002. However, an important limitation of substrates of natural or synthetic fibers such as cotton, polyester, polyethylene or the like is weakness making it necessary to use multiple layers of such substrate. Using multiple layers for more strength requires more time for forming or wrapping a cast or other structure and the hardened material is thick so as to be more uncomfortable and burdensome for the wearer and such thickness can impair the air permeability of the structure.